Olefin polymerization, especially ethylene polymerization, can benefit from the addition of longer-chain comonomers, such as 1-butene, 1-hexene, and 1-octene, to produce linear low density polyethylene (LLDPE). LLDPE produced from 1-butene, 1-hexene and 1-octene accounts for a large percentage of the polyethylene resin market. In general, polyethylene plants buy butene, hexene and octene, which are produced in separate plants that typically produce a range of even-numbered alpha olefins from ethylene. It can be expensive to purchase these materials, and they add to the complexity of transport, storage and handling. An attractive alternative is to make the comonomer directly from the ethylene at the site where they will be used, if this can be done cleanly and economically.
The review article “Advances in selective ethylene trimerisation—a critical review” by Dixon et al. (J. Organometallic Chemistry 689 (2004) 3641-3668), herein incorporated by reference in its entirety, describes many different catalysts for trimerization. These catalyst systems contain chromium, and with particular ligands, such as aromatic species (e.g., pyrrolyl) or multidentate heteroatomic species. The chromium catalysts are typically activated by alkylaluminum and/or alkyaluminoxane activators. The article also describes group 4 and 5 early transition metals, such as Zr, V, Ta and Ti, and group 8 late transition metals, such as Ni, for showing some activity in trimerization.
Phillips has developed chromium-based catalysts that are selective towards making 1-hexene from ethylene. The major byproduct appears to be 1-decene. SRI Consulting PEP Review 95-1-8 entitled “1-Hexene From Ethylene By the Phillips Trimerization Technology,” available on-line at http://www.sriconsulting.com/PEP/Reports/Phase—95/RW95-1-8/RW95-1-8.html, herein incorporated by reference in its entirety, describes the Phillips standalone process for making 1-hexene based on Phillips trimerization technology. In this process, ethylene and a homogeneous catalyst in a solvent are fed to a reactor. The reactor is a stirred tank with heat removal coils. This reactor operates at 115° C. and 49 kg/cm2 (˜700 psia), and converts about 75% of the ethylene fed. This reactor is 42,300 gal (5655 ft3). A spare reactor is provided, since waxy buildup on the cooling coils may necessitate lengthy shutdowns for cleaning. The feed is approximately 29,000 lb/hr cyclohexane solvent (with catalyst) plus 36,000 lb/hr ethylene (27,000 fresh feed and 9,000 recycle). It is estimated that the resident time in the reactor is on average 4 to 5 hours. Selectivity in the SRI process by weight is about 93% to 1-hexene, 1% to other C6's, 1% to octenes, and 5% to decenes. The effluent from the reactor is contacted with octanol to kill the catalyst from further reaction. The effluent then goes to an ethylene column where unconverted ethylene is taken overhead and recycled to the reactor. Because ethylene is so volatile, an expensive cryogenic column must be used. Four more distillation columns follow to remove hexene, cyclohexane solvent, octene, and decene. Some of these are run under vacuum, which again makes for expensive hardware and operations. The bottoms from the decene tower is a small stream containing mainly octanol and deactivated catalyst. This stream is treated with caustic and then with acid to remove the catalyst by precipitation and by solution in an aqueous phase, which is separated from the organic phase containing the octanol. Octanol may then be recycled.
U.S. Pat. No. 5,382,738 to Reagen et al., herein incorporated by reference in its entirety, discloses catalyst systems comprising inorganic oxides, modified with a metal alkyl and an unsaturated hydrocarbon, which can be used to support a metal source, such as, for example, chromium, and a pyrrole-containing compound. The resultant catalyst systems can be used to oligomerize and/or trimerize olefins via a slurry process.
U.S. Pat. No. 5,523,507 to Reagen et al., herein incorporated by reference in its entirety, discloses novel chromium-containing compounds prepared by forming a mixture of the chromium salt, a metal amide, and an ether either supported or unsupported. These novel chromium-containing compounds are activated by non-hydrolyzed alkyl aluminum compound and a Lewis acid.
U.S. Pat. No. 5,451,645 to Reagen et al., herein incorporated by reference in its entirety, discloses novel chromium-containing compounds prepared by forming a mixture of a chromium salt, a metal amide, and an ether. These novel chromium-containing, or chromium pyrrolide compounds, with a metal alkyl and an unsaturated hydrocarbon, can be used as a co-catalyst system in the presence of an olefin polymerization catalyst system to produce a comonomer in-situ with trimerization.
U.S. Pat. No. 5,543,375 to Lashier et al., herein incorporated by reference in its entirety, discloses a process to stabilize and/or reactivate an olefin production catalyst system, which comprises contacting an olefin production catalyst system, either before or after use, with an aromatic compound.
European Publication No. 0 668 106 to Freeman et al., herein incorporated by reference in its entirety, discloses a process which will effectively deactivate, inhibit, and/or “kill” an olefin production catalyst, and halt polymer production in an olefin production process. It further provides for a process which can remove an olefin production catalyst from the product stream, and recover catalyst by-products for recycle, and/or recovery.
International Publication No. WO 99/19280 A1 to Woodard et al., herein incorporated by reference in its entirety, discloses a process in which olefins are trimerized in the presence of a catalyst system comprising a chromium source, a pyrrole containing compound and a metal alkyl. The process is preformed in a reactor and provides for a separator for collection of the desired products.
International Publication Nos. WO 2004/056478 and WO 2004/056479, both to Blann et al., both hereby incorporated by reference in their entirety, disclose processes and catalysts to prepare an olefinic stream with more than 30% of 1-octene. The catalysts for this system are those that contain chromium or a chromium salt and a heteroatomic ligand.
A need exists for an improved process to generate alpha olefin comonomers. More particularly, a need exists for a reaction and separation process to generate 1-butene, 1-hexene, and/or 1-octene from ethylene for subsequent isolation or storage prior to being used in a polymerization reactor or other chemical process requiring such comonomer.
With regard to specific oligomerization catalyst systems, particularly ethylene trimerization systems, the following references are of interest: U.S. Pat. Nos. 3,333,016, 4,668,838, 5,137,994, 5,198,563, 5,382,738, 5,438,027, 5,439,862, 5,491,272, 5,523,507, 5,543,375, 5,744,677, 5,750,816, 5,750,817, 5,856,257, 5,856,612, 5,910,619, 5,968,866, 6,133,495, and 6,344,594; U.S. Patent Application Publication No. 2002/0035029 A1; International Publication Nos. WO 01/68572, WO 02/04119 (and related U.S. Pat. No. 6,800,702, as well as related U.S. Patent Application Publication Nos. 2003/166456 and 2005/020788), WO 02/066404, WO 02/083306, WO 03/004158, WO 03/053890, WO 04/056477, WO 04/056478, WO 04/056479, and WO 04/056480; European Publication Nos. EP 0 416 304 B1, EP 0 537 609, EP 0 608 447 B1, EP 0 614 865 B1, EP 0699648 B1, EP 0780353 B1, and EP 1110930 A1; Canadian Patent Nos. CA 2,087,578 and CA 2,115,639; Japanese Patent Publication Nos. JP 2001187345 A2 and JP 2001187345 A2; J. Am. Chem. Soc. 123, 7423-7424 (2001); McGuinness et al., J. Am. Chem. Soc. 125, 5272-5273, (2003); and Carter et al., Chem. Commun., 2002, pp. 858-859.
Likewise additional references regarding ethylene trimerization catalysts include: U.S. Pat. Nos. 3,333,016, 3,300,458, 4,472,525, 4,668,838, 4,689,437, 4,777,315, 4,853,356, 5,376,612, 5,382,738, 5,439,862, 5,523,507, 5,550,305, 5,557,026, 5,563,312, 5,668,249, 5,731,487, 5,744,677, 5,750,816, 5,750,817, 5,763,723, 5,811,618, 5,814,575, 5,856,257, 5,856,610, 5,856,612, 5,859,303, 5,910,619, 5,919,996, 5,968,866, 6,031,145, 6,133,495, 6,337,297, 6,344,594, 6,455,648, 6,521,806, 6,610,805, and 6,828,269; U.S. Patent Application Publication Nos. 2002/0035029, 2002/183574, 2003/130551, 2003/149198, 2004/122271, and 2004/228775; Chinese Publication No. CN 1256968; European Publication Nos. EP 622 347, EP 608 447, EP 706 983, and EP 1 110 930; British Patent No. GB 2298864; Japanese Publication Nos. JP 06-515873, JP 07-215896, JP 07-267881, JP 09-020692, JP 09-020693, JP 09-268133, JP 09-268134, JP 09-268135, JP 10-007593, JP 10-007594, JP 10-007595, JP 10-036431, JP 10-036432, JP 10-045638, JP 10-087518, JP 11-092407, JP 11-092408, JP 11-222445, JP 2000-176291, JP 2000-202299, JP 2000-212212, JP 2001-009290, JP 2002-045703, JP 2002-066329, JP 2002-102710, JP 2002-172327, JP 2002-200429, JP 2002-205960, JP 2002-233765, JP 2003-071294, JP 3351068 B2, JP 3540827 B2, JP 3540828 B2, and JP 3577786 B2; International Publication Nos. WO 97/37765, WO 01/10876, WO 01/47839, WO 01/83447, WO 02/83306, WO 03/004158, WO 03/053890, WO 03/053891, WO 04/056479, WO 04/056478, and WO 04/083263; Journal of Organometallic Chemistry 579 (1999) 45-52, Organometallics 1992, 11 3588-3600, Organometallics 1995, 14, 5652-5656, J. Chem. Soc., Perkin Trans. 1, 1999, 3177-3189, Organometallics 1994, 13, 2713-2720, Journal of Organometallic Chemistry, Volume 585, Issue 2, 15 Aug. 1999, pgs 225-233, Acta Cryst. (1991). C47, 23-26, Journal of Organometallic Chemistry, Vol 495, No. 1, 14 Jun. 1995, pgs 113-125, Inorg. Chim. ACTA (2000), 307(1-2), 47-56. Chem. Commun. 2005, 620-621, Chem. Commun. 2005, 622-624, Chem. Commun. 2005, 1865-1867, J. Am. Chem. Soc. 2004, 126, 14712-14713, J. Am. Chem. Soc. 2004, 126, 1304-1305, Macromolecules, 2004, 37, 9314-9320, Journal of Organometallic Chemistry, 2004, 689, 3641-3668, Heteroatom Chemistry, 1993, 4, 475-486; Synthesis, 1983, 1, 71-73; U.S. Pat. No. 6,800,702; Chem. Commun., 2002, 8, 858-859; PERP Report, Nexant/Chem Systems, 2004, 57-60; Dangadi Shiyou Shihu, 2002, 10, 25-29; ACS Symposium Series, 2002, 818, 147-160; Journal of Organometallic Chemistry, 2004689, 3641-3668; Journal of Catalysis, 1977, 47, 197-209; J. Am. Chem. Soc., 1989, 11, 674-675; Applied Catalysis, A (General) 2000, 193, 29-38; Hecheng Shuzhi Ji Suliao, 2001, 18, 23-25, 43; Organometallic Catalysts and Olefin Polymerization, 2001, 147-155; J. Mol. Catalysis A: Chemical (2002), 187, 135-141; J. Am. Chem. Soc., 2002, 125, 5272-5273; Chem. Commun. 2003, 3, 334-335; Beijing Huagong Daxue Xuebao, Ziran Kexueban, 2003, 30, 80-82; Adv. Synth. & Catalysis, 2003, 345, 939-942; Applied Catalysis, A: General, 2003, 255, 355-359; J. Am. Chem. Soc. 2004, 126, 1304-1305; ACS Symposium Series, 2003, 857 (Beyond Metallocenes), 88-100; and J. Am. Chem. Soc., 2004, 126, 14712-14713. Although the catalyst compositions in each of the above described references may be useful for the trimerization of ethylene, there remains a desire to improve the performance of olefin oligomerization catalysts from the standpoint of productivity and selectivity for oligomers such as 1-hexene or 1-octene, particularly where use in a commercial process, particularly an in-line process, is concerned.
Several pyridyl amine catalyst complexes have been disclosed for the polymerization or copolymerization of ethylene, propylene, isobutylene, octene, and styrene by Symyx Technologies, Inc. in U.S. Pat. Nos. 6,713,577, 6,750,345, 6,706,829, 6,727,361, and 6,828,397. Pyridyl amines were also disclosed in U.S. Pat. Nos. 6,103,657 and 6,320,005, assigned to Union Carbide Chemical and Plastics Technology Corporation, in which zirconium was used as the metal center, and the catalyst complex was used to polymerize alpha-olefins, and in U.S. Pat. No. 5,637,660, assigned to Lyondell Petrochemical Company, which also describes Group 4 complexes of pyridyl amine ligands. Robertson et al., Inorg. Chem. 42, pp 6875-6885 (2003), discloses chromium complexes of tris(2-pyridylmethyl)amine for ethylene polymerization.